1. Field of the Invention
The present invention relates to an ink, and an ink-jet recording method and instruments making use of the ink. More specifically, it relates to an ink which can provide prints excellent in water resistance and permits high-image quality recording using so-called plain paper such as acid paper and neutralized paper, which are commonly used in offices, and an ink-jet recording method and instruments making use of such an ink.
2. Related Background Art
Inks with greatly various manners of being composed have been hitherto reported in respect of inks for writing utensils (fountain pens, marking pens, ball-point pens making use of a water-based ink, etc.) and for ink-jet recording. In particular, in recent years, detailed researches and developments have been made from various aspects such as compositions and physical properties of inks because of a strong demand for improving the water resistance of prints making use of plain paper such as paper for copying, paper for reporting, notepaper and letter paper, which are commonly used in offices.
For example, Japanese Patent Application Laid-Open Nos. 2-296878 and 2-255876 have proposed to contain a polyamine in a water-based ink composition, thereby improving the water resistance of the resulting prints.
In such an ink, there is however a potential problem that clogging may occur, or the stability of the ink may be impaired because its basic mechanism of improving the water resistance is principally based on the formation of salt at the hydrophilic group site of a dye contained in the ink.
In the above-described ink, therefore, it has also been considered to contain a dissolution stabilizer in the ink for a purpose of improving the stability of the ink. In this case, however, it is necessary to contain a great amount of the dissolution stabilizer in the ink, so that the image quality of prints formed with such an ink becomes deteriorated.
In ink-jet recording, the fixing of an ink provided on a recording material such as plain paper is principally dependent on the natural penetration of the ink in the recording material and its evaporation, so that a problem of deterioration in image quality arises in particular.
Japanese Patent Application Laid-Open No. 57-577760 has proposed a method in which an amphoteric surfactant is contained in an ink to improve the water resistance of the resulting prints.
However, the above ink was such that the water resistance of prints formed therefrom was dependent on the kind of recording material to be used. More specifically, the ink had provided either prints excellent in water resistance or prints undue in image smearing and poor in water resistance depending on the surface pH, kind of sizing agent, kind of cellulose and the like of a recording material to be used.
Even if the ink could provide prints good in water resistance, it was poor in practicability in that it might become viscous, and clogging might occur. Besides, amphoteric surfactants generally contained many impurities therein, so that the reliability of the ink was lowered.
As described above, there has not yet been found an ink which can provide prints excellent in quality and water resistance, has excellent practicability, and can provide prints good in water resistance irrespective of materials of recording media.